i would say gainer, its just matter of do you have courage to do it :D for my first gainer i just watched somebody else do it and then i did it. i just run, and for my last step i start falling back and in the air i know that am i going to land it or not, if not i just tuck and land perfectly on my feet. its very easy trick because you can see water very soon. if you can, and want i would say that perfect height for first gainer is about 5-7 meters. if your about to do a standing gainer i cant help with that, still havent done that :D
hope this helped!